Carburetors for internal combustion engines



1 1967 A.-L. MENNESSON 3,346,245

CARBURBTORS FOR INTERNAL COMBUSTION ENGINES Filed Oct. 22, 1965 INVF/V TOR Inna: A cells MEmv: is aw 6 47' ,Mrm Y ATTORNEY United States Patent 3,346,245 CARBURETORS FOR INTERNAL COMBUSTION ENGINES Andr Louis Mennesson, Neuilly-sur-Seine, France, as-

signor to Societe Industrielle de Brevets et dEtudes S.I.B.E., Neuilly-sur-Seine, France, a society of France Filed Oct. 22, 1965, Ser. No. 501,759 Claims priority, application France, Nov. 16, 1964, 995,092 4 Claims. (Cl. 26161) The present invention relates to carburetors for internal combustion engines which comprise the following elements disposed, in an induction pipe, one behind the other in a direction opposed to that in which air is flowing through said pipe, to wit, a main throttle valve operated by the driver, a venturi into which is fed a main jet of fuel fed from a constant level chamber and an auxiliary throttle valve, or choke valve, adapted to be closed only when the engine is cold to increase the suction on said jet and consequently the flow rate thereof. The invention is more especially but not exclusively concerned with carburetors of the kind in question (called primary carburetors) which, in normal running conditions, work in parallel with carburetors of similar structure (called secondary carburetors) but which do not include an auxiliary throttle valve, the whole forming a compound carburetor device, the primary carburetor working alone when the engine is being started, with an output limited by the characteristics of its individual main jet system.

Such carburetors have already been provided with enrichment devices comprising a fuel circuit starting from the constant level chamber and opening into the induction pipe through an orifice (hereinafter called injection orifice) located upstream of the main jet system. Such enrichment devices increase the amount of fuel fed to the induction pipe by introduction of a metered supplementary fuel amount for high speeds, that is to say when the suction at the injection orifice (possibly weakened by the introduction of air) exceeds a value corresponding to the height of fuel between the constant level and said orifice.

Up to now, said injection orifice was located upstream of the auxiliary throttle valve or choke valve. As a matter of fact, if it were located downstream of said choke valve, the injection orifice would supply fuel not only at high speeds of the engine, which is desirable, but also, and irrespective of the engine speed, as long as the choke valve is not sufficiently open, due to the high suction that would be exerted on this orifice by an at least partial closing of said choke valve. This would result, When the engine is starting from cold, in an undesirable enrichment which might bedetrimental to the good operation of the engine and would anyway involve an unnecessary consumption of fuel.

However, it has been found that it was desirable to increase the flow rate of fuel not only for high speeds, but also when the engine is starting from cold, especially in the case of the above mentioned compound carburetor devices.

The object of the present invention is to provide a carburetor including an enrichment device better adapted to meet the requirements of practice than those used at the present time.

For this purpose, the carburator according to the present invention, which includes an enrichment device comprising of fuel circuit starting from the constant level chamber "and opening into the induction pipe through an injection orifice located upstream of the main jet of fuel, is characterized by the fact that said fuel injection orifice is located downstream of the auxiliary throttle valve, or choke valve, at least when the latter is closed, and by the fact that there is disposed, in said fuel circuit, an automatic closing device responsive to the suction existing in the induction pipe downstream of the main throttle valve, said automatic closing device being adapted to operate when said suction is greater, in absolute value, than a given limit and, consequently, to make the enrichment device inoperative when the engine is running under reduced load.

A preferred embodiment of the present invention will be hereinafter described with reference to the appended drawings, given merely by way of example, and in which:

FIG. 1 is a vertical sectional view of a carburetor made according to the present invention, in the position where the enrichment device is operative;

FIG. 2 is a partial view of the same carburetor in the position corresponding to the stopping of the enrichment device;

FIG. 3 shows a modification of a detail of the device of FIGS. 1 and 2; and

FIG. 4 shows a modification of other details of the carburetor of FIG. 1.

The carburetor of FIGS. 1 to 3 is of the down-draft type. It comprises, one behind the other in a direction opposed to that in which air is flowing through pipe 1, the following elements, to wit:

A main throttle valve 2 actuated by the driver;

A main venturi 3 into which opens a fuel jet device fed from a constant level chamber 4; and

An auxiliary throttle valve or choke valve 5 adapted to be closed only when the engine is cold.

Throttle valve 2 is shown in the form of a butterfly valve secured on a spindle 6 and actuated through a lever (not shown) fixed on said spindle 6. The main fuel jet device comprises a secondary, or boost, venturi 7, a conduit 8 and a well 9 which communicates at its bottom end with chamber 4, through a calibrated orifice 10, and at its upper end with the main air intake 11, through a calibrated orifice 12. A perforated tube 13 extends into well 9 to form a homogeneous mixture of the fuel and the air drawn through orifices 10 and 12 respectively. Chamber 4 contains a float 14a controlling a fuel inlet valve 14 and it is vented through a tube 15 from the air intake 11, which is preferably fitted with an air filter (not shown). Choke valve 5, which is located in said air intake 11, is eccentrically mounted on a spindle 16. This choke valve 5 is actuated through means, either manual or automatic, for closing it more and more as the engine is colder. For instance, as shown, this choke valve 5 is controlled through a lever operated by the driver.

The carburetor shown by the drawings, is branched on the intake pipe of the engine, possibly in shunt with a secondary carburetor, as above stated.

The carburetor according to the invention is provided with a fuel enrichment device comprising a fuel circuit starting from constant level chamber 4 and opening into the air intake 11 of induction pipe 1 through an injection orifice 17 located upstream of the main fuel conduit 8. Said fuel circuit essentially comprises two successive conduits 18 and 19, with calibrated metering orifice 20 at the outlet of conduit 18.

Now, according to the present invention, injection orifice 17 is located downstream of choke valve 5 and there is provided in circuit 18, 19, an automatic stopping device responsive to the suction existing in induction pipe 1 downstream of main throttle valve 2 (at least when this last mentioned ,valve is closed) this automatic stopping device beingadapted to become operative when said suction is greater (in absolute value) than a predetermined limit. This stopping device consists, in the embodiment illustrated by-the drawings, of a valve 21 cooperating with a seat 22 and controlled by a diaphragm 23 subjected to said-suction. This diaphragm 23 forms a chamber 24 is connected, in an intermittent manner, with conduit 18 through seat 22 and,.in a permanent manner, WltlilpCOIldUlt 19. The-second chamber 25 is connected through a conduit 26 with a 'pointof'induction pipe '1 located downstream of themainthrottle valve 2 (at least When thersuction acting upon orifice 17 produces in conduit 19 a resultant suction corresponding, in height-- 1 of fuel, to the level difference H, orifice 17 starts deliverwhen said valve is closed) and it contains a spring 27 urging valve 21 away from its seat '22.

In order to reduce the suction transmitted through orifice 17 to the enrichment circuit 18, 19, there is provided a'bleed conduit 28 :or 28a of small cross section opening into fuel conduit 19, and starting from the air intake 11. As shown by FIGS. 1 and 2, the inlet end of conduit 28 is located always downstream of choke valve 5.

However, in some other cases, it may be of interest, as shown by FIG. 3, to have the inlet end of conduit 28a located in such manner that it passes from the downstream side to the upstream side of choke valve when the latter is brought into the closed position illustrated by said FIG. 3.

This carburetor Works as follows: a

When the engine is cold and at rest, the parts occupy the positions illustrated by FIG. 1 and more particularly those illustrated in dot-and-dash lines for throttle valves 2 and 5. Choke valve 5 is kept closed against the action Valve 21 is kept away from its seat 22 by spring 27 so 7 that conduit 19 is in communication with conduit 18.

If now the engine is started, the strong suction corresponding to the closed position of choke valve Scauses fuel to spout not only from the conduit 8 of the main jet system but also through injection orifice 17 and, possibly, through conduit 28 (FIGS.-1 and 2). If the calibrated metering orifice 10 is insufficient to'ensure by itself the flow of fuel suitable for starting, orifice 17 and,

possibly, conduit 28 ensure the necessary supplementary flow raterAccording to the modification of FIG. 3, which corresponds to the case where the sum of the flow rates through orifices 10 and 17 would be execessive, the air sucked in through conduit 28a reduces the suction acting in circuit 18, 19 and consequently the flow rate entering induction pipe 1 through orifice 17 As soon as the engine in the cold state is started, the

. elements of the carburetor come into the positions of FIG. 2. Choke valve 5 opens slightly, in such manner as to reduce the suction existing in venturi 3 and consequently the flow rate of fuel through conduit 8. At the same time, as the suction existing downstream of the 'main throttle valve has increased, diaphragm 23 is moved '(which constitutes the above mentioned limit) in chamber 25.

When the engine is warm, choke valve 5 opens fully, as shown in solid lines in FIG. 1.

For high speeds of rotation of the engine and in the V vicinity :of the maximum power, the enrichment device then acts to modify the shape of the full load curve by, enriching in fuelthe air fuel mixture sucked in by the engine in the following manner.

The fuel level, which is normally in conduit 19 and in chamber 24 at the same level'N as in constant level chamber 4, is subjected to a suction acting upon orifice 17 and which may be slightly reduced by the provision of conduit 28. e

This suction which, due to the position of orifice 17,

is a dynamic suction, increases with the 'air flow rate and is anyway greater than that exerted at the inlet of tube 15 which has its orifice turned toward the air inlet.

ing a fuel supplement producing an enrichment of the mixture that is sucked in. On the contrary, with reduced loads, where this enrichment is not necessary, the suction in conduit 26 closes valve 21 and prevents any possiblity of delivery of fuel through orifice 17. V 7

Generally (in the absence of conduit 28 or 28a), the height H corresponds to a suction existing for about 3000 revolutions per minute on the full load curve of the engine. Therefore, from 3000 revolutions per minute and for higher speeds, orifice 17 delivers fu'el whereas, for lower speeds (and with the choke valve open) it does not deliver any fuel. V

It is in the case where it is desired to have fuel delivered through orifice 17 for a speed higher than 3000 revolutions per minute (that is to say for a suction higher than that corresponding to height H) that conduit 28 or 28a is provide. By a suitable choice of the ratio at the respective sections of this conduit 28 or 28a and of orifice 17, it is possible to determine any desired value (higher than that corresponding to height H) of the suctionat' the level of this orifice for which fuel starts spouting therefrom. V a To sum up, the enrichment device is brought into play not only at high speeds of the engine, but also when it is started from cold. 7 j H Of course, the. invention is applicable to carburetors other than a down-draft one..For instance, FIG. 4 illustrates a carburetor of another kind where the elements playingythe same part as those of FIG. 1 are designated by the same reference numerals. Attention is called to the fact that in FIG. 4 the boost venturi 70f FIG. 1 does V not exist. Orifice 17 must be located at a height H above arrangement, disposition and form of the parts without.

departing from the principle of the invention as comprebended withinthe scope of the appended claims.

What I claim is:

1. For use in connection with an internal combustion engine, a carburetor which comprises, in combination,

an induction pipe,

;a main throttle valve to be controlled by the driver, lo-Q cated in said induction pipe,

a venturi located in said main pipe upstream of said main throttle valve,

a fuel constant level chamber mounted in fixed position with respect to said induction pipe,

means for feeding a jet of fuel from said constant level chamber into said venturi,

a choke valve located in said main pipe upstream of said venturi adapted to be closed more and more as the engine is colder, and

" a device for enriching in fuel the air and fuel mixture supplied by said carburetor, said device including,

a fuel injection orifice opening into said induction pipe upstream of the output therein of said means for feeding a jet of fuel and downstream of said choke stream of said main throttle valve, said stopping means including means to cut off the fuel flow through said fuel circuit when said suction is greater, in absolute value, than a given limit, and conduit means extending between said fuel circuit and the portion of said induction pipe immediately downstream of said choke valve.

2. A carburetor according to claim 1 wherein said fuel stopping means include a valve seat in said fuel circuit,

a valve adapted to cooperate with said valve seat to open or close it,

means forming a chamber in communication with said induction pipe in a portion thereof downstream of said main throttle valve,

means forming a chamber in communication with said fuel circuit,

a flexible diaphragm forming a separation between said two last mentioned chambers,

said flexible diaphragm being operatively connected with said last mentioned valve, and

spring means interposed between said diaphragm and one of said two last mentioned means for urging said valve away from its seat.

3. For use in connection with an internal combustion engine, a carburetor which comprises, in combination,

an induction pipe,

a main throttle valve to be controlled by the driver,

located in said induction pipe,

a venturi located in said main pipe upstream of said main throttle valve,

a fuel constant level chamber mounted in fixed position with respect to said induction pipe,

means for feeding a jet of fuel from said constant level chamber into said venturi,

a choke valve located in said main pipe upstream of said venturi adapted to 'be closed more and more as the engine is colder, and

a device for enriching in fuel the air and fuel mixture supplied by said carburetor, said device including,

a fuel injection orifice opening into said induction pipe upstream of the output therein of said means for feeding a jet of fuel and downstream of said choke valve in the closed position thereof,

a fuel circuit extending from said fuel constant level chamber to said fuel injection orifice,

fuel stopping means in said fuel circuit responsive to the suction existing in said induction pipe downstream of said main throttle valve, said stopping means including means to cut off the fuel flow through said fuel circuit when said suction is greater, in absolute value, than a given limit, and

conduit means extending between said fuel circuit and a point of said induction pipe located downstream of said choke valve when the latter is open and upstream of said choke valve when the latter is closed.

4. A carburetor according to claim 3 wherein said fuel stopping means include:

a valve seat in said fuel circuit,

a valve adapted to cooperate with said valve seat to open or close it,

means forming a chamber in communication with said induction pipe in a portion thereof downstream of said main throttle valve,

means forming a chamber in communication with said fuel circuit,

a flexible diaphragm forming a separation between said two last mentioned chambers,

said flexible diaphragm being operatively connected with said last mentioned valve, and

spring means interposed between said diaphragm and one of said two last mentioned means for urging said valve away from its seat.

References Cited UNITED STATES PATENTS 2,389,922 11/1945 Mennesson 261-69.1 2,611,592 9/1952 Anderson 261169 X 2,977,948 4/ 1961 Kittler 26169 X HARRY B. THORNTON, Primary Examiner.

RONALD R. WEAVER, Examiner. 

1. FOR USE IN CONNECTION WITH AIN INTERNAL COMBUSTION ENGINE, A CARBURETOR WHICH COMPRISES, IN COMBINATION, AN INDUCTION PIPE, A MAIN THROTTLE VALVE TO BE CONTROLLED BY THE DRIVER, LOCATED IN SAID INDUCTION PIPE, A VENTURI LOCATED IN SAID MAIN PIPE UPSTREAM OF SAID MAIN THROTTLE VALVE, A FUEL CONSTANT LEVER CHAMBER MOUNTED IN FIXED POSITION WITH RESPECT TO SAID INDUCTION PIPE, MEANS FOR FEEDING A JET OF FUEL FROM SAID CONSTANT LEVEL CHAMBER INTO SAID VENTURI, A CHOKE VALVE LOCATED IN SAID MAIN PIPE UPSTREAM TO SAID VENTURI ADAPTED TO BE CLOSED MORE AND MORE AS THE ENGINE IS COLDER, AND A DEVICE FOR ENRICHING IN FUEL THE AIR AND FUEL MIXTURE SUPPLIED BY SAID CARBURETOR, SAID DEVICE INCLUDING, A FUEL INJECTION ORIFICE OPENING INTO SAID INDUCTION PIPE UPSTREAM OF THE OUTPUT THEREIN OF SAID MEANS FOR FEEDING A JET OF FUEL AND DOWNSTREAM OF SAID CKOKE VALVE IN THE CLOSED POSITION THEREOF, A FUEL CIRCUIT EXTENDING FROM SAID FUEL CONSTANT LEVEL CHAMBER TO SAID FUEL INJECTION ORIFICE, FUEL STOPPING MEANS IN SAID FUEL CIRCUIT RESPONSIVE TO THE SUCTION EXISTING IN SAID INDUCTION PIPE DOWNSTREAM OF SAID MAIN THROTTLE VALVE, SAID STOPPING MEANS INCLUDING MEANS TO CUT OFF THE FUEL FLOW THROUGH SAID FUEL CIRCUIT WHEN SAID SUCTION IS GREATER, IN ABSOLUTE VALUE, THAN A GIVEN LIMIT, AND 